1. Field of Invention
This present invention relates to micromachined or microelectromechanical system (MEMS) based fluid ejectors.
2. Description of Related Art
Fluid ejectors have been developed for ink jet recording or printing. Ink jet printing systems offer numerous benefits, including extremely quiet operation when printing, high speed printing, a high degree of freedom in ink selection, and the ability to use low-cost plain paper. The so-called xe2x80x9cdrop-on-demandxe2x80x9d drive method, where ink is output only when required for printing, is now the conventional approach. The drop-on-demand drive method makes it unnecessary to recover ink not needed for printing.
Fluid ejectors for ink jet printing include one or more nozzles which allow the formation and control of small ink droplets to permit high resolution, resulting in the ability to print sharper characters with improved tonal resolution. In particular, drop-on-demand ink jet print heads are generally used for high resolution printers.
Drop-on-demand technology generally uses some type of pulse generator to form and eject drops. For example, in one type of print head, a chamber having an ink nozzle may be fitted with a piezoelectric wall that is deformed when a voltage is applied. As a result of the deformation, the fluid is forced out of the nozzle orifice as a drop. The drop then impinges directly on an associated printing surface. Use of such a piezoelectric device as a driver is described in JP B-1990-51734.
Another type of print head uses bubbles formed by heat pulses to force fluid out of the nozzle. The drops are separated from the ink supply when the bubbles form. Use of pressure generated by heating the ink to generate bubbles is described in JP B-1986-59911.
Yet another type of drop-on-demand print head incorporates an electrostatic actuator. This type of print head utilizes electrostatic force to eject the ink. Examples of such electrostatic print heads are disclosed in U.S. Pat. No. 4,520,375 to Kroll and Japanese Laid-Open Patent Publication No. 289351/90. The inkjet head disclosed in the 375 patent uses an electrostatic actuator comprising a diaphragm that constitutes a part of an ink ejection chamber and a base plate disposed outside of the ink ejection chamber opposite to the diaphragm. The inkjet head ejects ink droplets through a nozzle communicating with the ink ejection chamber, by applying a time varying voltage between the diaphragm and the base plate. The diaphragm and the base plate thus act as a capacitor, which causes the diaphragm to be set into mechanical motion and the fluid to exit responsive to the diaphragm""s motion. On the other hand, the ink jet head discussed in the Japan 351 distorts its diaphragm by applying a voltage to an electrostatic actuator fixed on the diaphragm. This result in suction of additional ink into an ink ejection chamber. Once the voltage is removed, the diaphragm is restored to its non-distorted condition, ejecting ink from the overfilled ink ejection chamber.
Fluid drop ejectors may be used not only for printing, but also for depositing photoresist and other liquids in the semiconductor and flat panel display industries, for delivering drug and biological samples, for delivering multiple chemicals for chemical reactions, for handling DNA sequences, for delivering drugs and biological materials for interaction studies and assaying, and for depositing thin and narrow layers of plastics for usable as permanent and/or removable gaskets in micro-machines.
This invention provides fluid ejection systems and methods having improved performance characteristics.
This invention separately provides fluid ejection systems and methods having improved response to actuation signals and/or improved control.
This invention separately provides fluid ejection systems and methods having improved efficiency.
This invention separately provides fluid ejection systems and methods having improved electrostatic fields.
This invention separately provides fluid ejection systems and methods having improved fluid refill.
This invention separately provides fluid ejection systems and methods having increased drop generation rate.
This invention separately provides fluid ejection systems and methods having reduced viscous fluid forces that oppose refill of the fluid after ejection.
This invention separately provides fluid ejection systems and methods where the viscous fluid forces opposing movement of the actuator used to eject the fluid prevent the actuator from contacting other structures of the ejector.
This invention separately provides fluid ejection systems and methods having fluid ejectors with improved structural features.
This invention separately provides fluid ejection systems and methods having fluid ejectors with simplified design, construction and fabrication.
In various embodiments, the fluid ejectors according to this invention include an unsealed movable piston structure usable to eject fluid drops. In other various embodiments, the fluid ejectors according to this invention provide unimpeded fluid flow adjacent the piston structure in a direction transverse to the direction of movement of the piston structure. In still other various embodiments, the fluid ejectors according to this invention include a counter-electrode.
According to various exemplary embodiments of the systems and methods of this invention, a micromachined fluid ejector includes a movable piston structure arranged to eject fluid drops. The piston structure is resiliently movably supported within a fluid chamber, such that movement of the piston structure ejects fluid. In various embodiments, the fluid chamber is defined between a substrate and a faceplate including a nozzle hole such that transverse fluid flow is substantially unrestricted near the piston structure. In other various embodiments, the fluid ejectors according to this invention include an ink feed hole formed through the substrate.
These and other features and advantages of this invention are described in, or are apparent from, the following detailed description of various exemplary embodiments of the systems and methods according to this invention.